1. Field of the Invention
This invention relates to metal bonding using explosive energy. More specifically, the invention is an apparatus and method for explosive bonding between a flyer plate and a base plate to achieve a bond to the edge of the flyer plate.
2. Description of the Related Art
Demand is increasing for highly reliable, remote, metal joining of plates at low initial investment for inaccessible operations such as assembly of structures in space and fabrication of hermetic seals in small areas. Prior art methods, such as mechanical fasteners, swaging fusion welding, soldering, and adhesives have been inadequate due to constraints to hand operations, inaccessibility of the parts to be joined, insufficient strength and resistance to environments, particularly high temperatures. Only explosive joining offers the characteristics to meet the above requirements. This type of joining produces metallurgical bonds that the other processes cannot achieve. The explosive joining process creates a high velocity, angular collision between the metal surfaces, which causes formation of interatomic, electron-sharing linkups.
Previous methods of explosive joining, however, have limited suitability because they require using relatively large amounts of explosive, which results in an inability to locate precisely the limits of the bonded area. Repeated joining cycles of the previous art, all using the exact same setup, result in varied bond areas and require sophisticated test methods, such as ultrasonic nondestructive testing, to determine the limits of the bond. Thus, to assure the bond area extends to a prescribed limit, conventional joining processes must overlap the bond beyond the prescribed limit and then remove the overlap.
For example, the prior art disclosed in U.S. Pat. No. 3,940,049, by Richter et al, anticipates removal of the unbonded flyer plate and suggests various methods for leaving a region of the flyer plate unbonded. These methods include leaving the intended unjoined zones free of explosive, using a separating agent such as grease to prevent the bonding, or oxidizing the intended unjoined zones by electrolysis prior to the explosive bonding. Richter also proposes upwardly bending the flyer plate after bonding to allow for machining of the base plate, but never hints at fracturing the flyer plate to provide a bond to its edge. Removal of the outer extremity of the unbonded flyer plate through machining or grinding is difficult, particularly at the joining site, and may damage the surface of the base plate.
Previous methods of explosive joining have limited suitability also because the large amounts of explosive present problems in safe handling and operation. Impacts, electrical shocks, heat, and fire may ignite the explosive and subsequently increase the hazards of operation. Large amounts of explosive may also result in damage to lightweight structures such as thin plates.